1. Field of the Invention
This invention is directed toward an improved, snubbed, pivot connection.
2. Description of the Prior Art
Grapples are employed in loading or skidding logs in the forest industry. The grapple has a pair of grapple arms pivotally suspended from the end of a boom, the arms operable to grapple or grab a load of logs. The pivot connection connecting the grapple arms to the boom comprises two pivots, with the axis of the two pivots at right angles to each other to permit universal movement of the grapple arms. To prevent the grapple arms from swinging uncontrollably about the pivots, which swinging could cause damage and/or injury, and which causes excessive wear on the pivots, dampers or snubbers are provided in the pivots to dampen the swinging movement.
Each pivot usually employs a link member pivotally connected by a pivot pin between the arms of a yoke member. The snubber employed is usually a dual snubber having a pair of opposed brake means in the pivot to balance the braking load and reduce wear. Examples of such dual snubbers are shown in U.S. Pat. No. 4,572,567, Johnson, issued Feb. 25, 1986, and in U.S. Pat. No. 4,573,728, Johnson, issued Mar. 4, 1986, by way of example. These dual snubbers are usually operated by hydraulic means. The use of fluid to actuate the brake means in the dual snubber presents a problem in that the fluid leaks. Leakage of fluid changes the braking effect. In addition, the hydraulic actuating means employed in these dual snubbers are often complicated in construction and thus expensive. The known dual snubbers also have wear problems due to the type of brake means employed. Brake disks, as employed in U.S. Pat. No. 4,573,728, for example, wear unevenly because it is difficult to apply pressure uniformly. Often the brakes are quite small, as in U.S. Pat. No. 4,572,567, for example, and thus tend to wear out quite quickly because of the load applied.
It is known to provide snubbers that are mechanically rather than hydraulically operated. These single snubbers employ a tapered brake sleeve in the brake means cooperating with a tapered braking surface. These brake means increase the braking efficiency because of their size, and being self-centering, braking force is applied more evenly, thus reducing wear of the brake means. The tapered brake sleeve, being operated mechanically rather than hydraulically, ensures that the braking force remains more constant. Examples of such snubbers are shown in U.S. Pat. No. 5,451,087, Beaulieu, issued Sep. 19, 1995. However, these single snubbers do not provide balanced braking and thus have excessive wear. In addition, the adjustment means employed to control their braking force are still quite complicated and thus expensive. Further, the single snubbers require enlarged yokes to be properly used in some embodiments, and in other embodiments, the single snubbers are exposed to damage.
Other examples of double mechanically operated snubbers are found in U.S. Pat. No. issued Feb. 3, 1998. These double snubbers are an integral part of the load bearing structure at the pivot connection and subject to uneven wear of the breaking surfaces leading to a reduced dampening ability of the snubber.